1. Technical Field
Exemplary aspects of the present invention generally relate to an image forming apparatus such as a copier, a printer, a facsimile, or a multi-functional system including a combination thereof, and more particularly, to an image forming apparatus using an intermediate transfer member.
2. Description of the Related Art
There is known an image forming apparatus equipped with an image bearing member bearing a visible image known as a toner image and a nip forming member that contacts the image bearing member to form a so-called a transfer nip therebetween. In the transfer nip, the toner image is transferred onto a recording medium. In such an image forming apparatus, in order to prevent deformation and contamination of the image bearing member and the nip forming member, the nip forming member is separated from the image bearing member in cases other than an image forming operation. The nip forming member contacts the image bearing member during the image forming operation.
For example, JP2010-019964-A proposes a moving device disposed coaxially on a rotary shaft of an image bearing member supported rotatably about the rotary shaft. The rotary shaft is rotatably driven by a first drive source, and the moving device is rotatably driven by a second drive source via a drive transmission device.
In such a configuration, parts employed in the drive transmission device have different tolerances and assembly variations. As a result, backlash or play in the direction of rotation may be generated. When a plurality of gears is employed as a drive transmission device, the gears contact at the upstream side (drive source side) in a drive transmission path and rotate. Accordingly, the moving device disposed at the end of a drive transmission path has backlash only in a forward direction in the direction of rotation.
Because the moving device and the image bearing member are disposed coaxially on the same rotary shaft, while the nip forming member and the image bearing member are separated and the rotary shaft rotates in the same direction as the direction of rotation of the moving device, the frictional force between the moving device and the rotary shaft or the rotary member supported by the rotary shaft causes the moving device to rotate by the amount of backlash. As long as a certain amount of space is secured between a transfer device and the image bearing member even after the moving device rotates by the amount of backlash, rotation of the moving device does not cause an adverse effect. However, when there is a significant amount of backlash, a sufficient amount of space may not be secured between the transfer device and the image bearing member.
In view of the above, there is thus an unsolved need for an image forming apparatus capable of preventing undesirable rotation of the moving device and hence securing reliably a space between the transfer device and the image bearing member.